When EL (electroluminescence) elements are used for products in the field of lighting or the like, there is a problem of shorts (short circuits) between their anode and cathode. Particularly, since organic EL lighting has a large light-emitting area to which an electric field is applied, there is a high probability of causing shorts, and this results in low yield and low reliability.
As a measure of the shorts, there is a repair method using laser light as disclosed in Patent Document 1. Specifically, for example, as the repair method, there is a method of conducting about 100-hour lighting for aging prior to shipment and repairing the portions where shorts are caused or shorts are not yet caused but bright points are found using laser light or the like. This method employs a technique that continuously turns on organic EL elements by a forward bias and then locally breaks down to open or insulate the portions where shorts are caused. However, in such a repair method, products need to be energized until shorts have not caused for a predetermined long period so as to improve their reliability. Also, equipment and space will be required for all products that are to be aged.
As another repair method using laser light, there is a method of applying a forward voltage that is equal to or lower than the voltage for causing a normal element (in which no shorts are caused) to emit light, causing the portions that are thinner than normal portions to emit weak light, recognizing their images, and repairing them by using laser light.
On the other hand, as a repair method without using laser light, for example, there is a method of applying a reverse bias direct current (DC) to elements and locally repairing the portions that are thinner than normal portions by a reverse current. However, since the applicable voltage is low in this repair method, there is a problem that a number of portions among the portions where shorts can be caused would remain unrepaired. Therefore, the repair method using laser light is commonly employed.